Are you using ngTouch in your app? Your code works for me & autofocuses on Chrome on Android if ngTouch isn't loaded in the app, but if ngTouch is used, not only does it not work, sometimes it makes the input completely unfocusable by de-focusing as the input is manually clicked on. [facepalm]

As @jorisw mentioned, I don't think its possible to get autofocus to work on any iOS devices - the input is focused, but the on-screen keyboard doesn't appear, so the user has to manually click the input.